Scientists

Do you wish you could forget that time singing karaoke with your boss or recall the location of that great restaurant you visited last year? Take heart: Scientists are coming closer to being able to turn memories on and off with the flip of a switch. A team led by Theodore Berger, a professor of biomedical engineering at USC, has figured out how to manipulate brain cells in rats so that memories stored in the hippocampus, a region crucial for memory formation, were activated or suppressed.

Let that long-held breath out, folks. The Alpha Magnetic Spectrometer has picked up a lot of mysterious antimatter in low Earth orbit - but that doesn't necessarily mean it's a sign of dark matter. In fact, even with the 400,000 positrons picked up by the cosmic-ray experiment -- the largest number of such particles ever analyzed in space -- it's unclear whether those positrons result from decaying dark matter, or simply from pulsars sending particles into the universe. "What you have probably seen from the data is a significant new measurement," said Brown University physicist Richard Gaitskell, a lead scientist on a different dark matter detector called the Large Underground Xenon experiment.

Do polar bears face obliteration as a species, not from starvation as the northern ice melts but through interbreeding with brown bears as changes in the climate bring them into contact with each other? Authors of a new report say that's a distinct possibility. The closest relative of the polar bear is the brown bear - matings between grizzlies and polar bears sometimes happen  in zoos or the wild, yielding very rare examples of hybrids known as grolar bears or pizzlies. Webb Miller of Pennsylvania State University and colleagues set out to examine the timing of the divergence between the two species, using a whole mess of DNA data - from contemporary brown bears, polar bears and black bears as well as from a polar bear that lived 110,000 to 130,000 years ago. (The ancient DNA was obtained from a jawbone found in Norway.)

Nothing new in the world? Nothing left to discover? NASA would beg to differ. The discovery of an "enormous, off-the-charts" bloom of microscopic marine plants in the Arctic has floored scientists. And it confirms, if nothing else, that there are things on this planet not yet seen -- things that you "never, ever could have anticipated in a million years. "  So says Paula Bontempi of NASA. An ocean biology and biogeochemistry program manager in Washington, Bontempi spoke with the Los Angeles Times on Friday morning about the discovery.  Here's how it came about: Over the summers of 2010 and 2011, NASA's Icescape expedition was exploring the Arctic waters of the Beaufort and Chukchi seas off Alaska.

The dark dust thrown up by human activity in the deserts of the Southwest hastens the melting of Rocky Mountain snow and ultimately reduces the amount of water flowing into the upper Colorado River by about 5%, scientists reported Monday. The lost water amounts to more than 250 billion gallons — enough to supply the Los Angeles region for 18 months, said study leader Thomas H. Painter, a snow hydrologist at the Jet Propulsion Laboratory in La Cañada Flintridge. "That's a lot of water," said Painter, whose study was published online by the Proceedings of the National Academy of Sciences.

A team of storm-chasing scientists sampling rarefied air has found a world of bacteria and fungi floating about 30,000 feet above Earth. The findings, detailed Monday in the Proceedings of the National Academy of Sciences, suggest that microbes have the potential to affect the weather. Scientists have long studied airborne bacteria, but they typically do so from the ground, often trekking to mountain peaks to examine microbes in fresh snow. Beyond that, they don't know much about the number and diversity of floating microbes, said study coauthor Athanasios Nenes, an atmospheric scientist at Georgia Tech.

Have scientists finally discovered the genetic fountain of youth? Hardly. But by creating a genetic switch that allows them to artificially age — and rejuvenate — lab mice, scientists have shown that it is possible to reverse some effects of aging in mammals. "It indicates there's a point of return if you remove the underlying cause of the aging," said Dr. Ronald DePinho, the molecular biologist at the Dana-Farber Cancer Institute at Harvard Medical School who led the study, published online this week in the journal Nature.

In August, NASA's Mars Science Laboratory will reach the Red Planet and begin its search for habitats that could have supported life. The next-generation rover, better known by the nickname Curiosity, will pick its way up a mound in the middle of Gale crater and look for evidence that water once flowed on the Martian surface - a condition that is considered a prerequisite for hosting microbial beings. On an expedition to the California desert this month to demonstrate some of the challenges Curiosity will face on Mars, scientists chatted about the upcoming mission.

Is 2012 the end of the world? If you scan the Internet or believe the marketing campaign behind the movie "2012," scheduled for release in November, you might be forgiven for thinking so. Dozens of books and fake science websites are prophesying the arrival of doomsday that year, by means of a rogue planet colliding with the Earth or some other cataclysmic event. Normally, scientists regard Internet hysteria with nothing more than a raised eyebrow and a shake of the head. But a few scientists have become so concerned at the level of fear they are seeing that they decided not to remain on the sidelines this time.

The catch of small, schooling fish such as sardines and anchovies should be cut in half globally and the amount left in the ocean doubled to protect the ecologically vital species from collapse, scientists say in a new report. The silvery species known as forage fish are harvested in huge numbers worldwide and are easy for fishermen to round up because they form dense schools, or "bait balls. " But wide fluctuations in their numbers make them especially vulnerable to overfishing, according to the report released Sunday by the Lenfest Forage Fish Task Force, a 13-member panel of scientists from around the world.